Nepheline syenite
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Nepheline syenite is a coarse crystalline igneous rock composed primarily of orthoclase alkali-feldspars, nepheline and mafic minerals such as the sodium rich pyroxenes and amphiboles. Accessory minerals are other sodium-feldspathoids, zircon, apatite and sphene. Nepheline syenites occur in Canada, Norway, Greenland, Sweden, the Ural Mountains, the Pyrenees, Italy, Brazil, China, the Transvaal region, and Magnet Cove area of Arkansas.
References
- Nepheline in Arkansas (http://www.state.ar.us/agc/nephelin.htm)
- Canada fact sheet Nepheline syenite (http://mmsd1.mms.nrcan.gc.ca/mmsd/producers/factsheets/nepheline_syenite_e.asp)
- USGS (http://vulcan.wr.usgs.gov/LivingWith/VolcanicPast/Notes/syenite.html)Template:Geol-stub